NASA Probe Looks at Bright Side of Mars

by SPACE.com Staff | July 03, 2009 09:55am ET

Pastel colors swirl across Mars, revealing differences in the composition and nature of the surface in this false-color infrared image taken on May 22, 2009,by the Thermal Emission Imaging System (THEMIS) camera on NASA's Mars Odyssey orbiter.Credit: NASA/JPL/ASU

An aging but dependable NASA
probe has tweaked its orbit around Mars to seek out warmer ground on the distant,
red world.

NASA reckons the infrared
cameras aboard the Mars Odyssey spacecraft will work better over regions
exposed to more sunlight, so it shifted the probe?s orbit in order to steer its
camera eyes away from the evening shade. The move took nearly eight months, ,
but Odyssey?s infrared camera now peers onto the planet during the Martian
afternoon, earlier than it has during most of its seven-year mission.

"The orbiter
is now overhead at about 3:45 in the afternoon instead of 5 p.m., so the
ground is warmer and there is more thermal energy for the camera's infrared
sensors to detect," said Jeffrey Plaut planetary scientist at NASA's Jet
Propulsion Laboratory (JPL) in Pasadena, Calif., in a statement.

The orbital switch increases
the sensitivity of the camera, called the Thermal
Emission Imaging System, to allow for better mapping of Martian minerals.
It now senses infrared radiation from a warmer surface that is receiving more
sunlight.

A warmer Martian target

Temperatures on Mars range
from as low as minus 195 degrees Fahrenheit (-125 degrees Celsius) near the
poles during the winter to 70 degrees Fahrenheit (20 degrees Celsius) at noon
near the equator. The average Martian temperature is about? minus 80 degrees
Fahrenheit (-60 degrees Celsius).

On Sept. 30, 2008, Odyssey
fired its thrusters for six minutes, entering into a "drift"
pattern that gradually changed its orbit and the time-of-day during which it
was over the planet. On June 9 of this year, the spacecraft fired the thrusters
again, this time for 5.5 minutes. The burn ended the drift pattern and locked
the spacecraft into the new orbit, always above the planet in the
mid-afternoon.

"The maneuver went
exactly as planned," said JPL's Gaylon McSmith, Odyssey mission manager.

Afternoons on Mars

This is not the first time
the orbiter will see a sunnier side of Mars. Back in 2002, early in Odyssey's
mission, it flew mid-afternoon passes over the planet and made important
discoveries of minerals, including salt deposits that were apparently left
behind by large bodies of water when they evaporated.

"The new orbit means we can now get the type of high-quality data for the
rest of Mars that we got for 10 or 20 percent of the planet during those early
six months," said Philip Christensen, an Arizona State University
researcher who is principal investigator
for Odyssey's Thermal Emission Imaging System.

The trade-off is that the
new orbit will put one of the spacecraft's other instruments out of commission.
The gamma-ray detector, one of a suite of three instruments that sense short
light waves and neutrons, must be shut down or risk overheating. In 2002, the
suite, called the Gamma Ray Spectrometer, made a dramatic discovery of large
areas of water-ice near the Martian surface. The gamma ray detector has also
mapped the global deposits of many elements, such as iron, silicon and
potassium.

NASA launched the Mars
Odyssey orbiter in 2001. The solar-powered spacecraft arrived at the red planet
about a year later to begin its now seven-year Mars observation campaign.